The objective of this proposal is to maintain a closed specific pathogen-free (SPF) rhesus macaque breeding colony program at the Sabana Seca Field Station of the Caribbean Primate Research Center (CPRC). The founding stock of genetically-characterized Indian-origin monkeys will be donated by CPRC and consists of approximately 300 SPF rhesus macaques. Animals from this closed colony will be housed in reproduction corncribs, and will be quarterly tested for the presence of four target viruses (Herpes B, STLV-1, SIV and SRV). To characterize the colony and to optimize the structure of its breeding groups, a panel of highly polymorphic genetic markers will be used maximizing the level of their genetic heterogeneity. It is projected the program will produce a total offspring of 584 SPF rhesus macaques to help meet the increased demand for these animals. At the end of this grant, it is expected that this program will produce and will make available to PHS-funded investigators about 180 MHC typed SPF animals/year, thus attaining self-sufficiency. CPRC will continue to make significant contributions to AIDS and to other research programs by providing high quality and healthy SPF rhesus monkeys to NIH-sponsored research projects.